1. Field of the Invention
The present invention relates to a chemical mechanical polishing method and a chemical mechanical polishing device for performing a flattening process on an interlayer insulating film formed by coating a projecting pattern on a substrate.
2. Description of the Related Art
Chemical mechanical polishing (hereinafter, “CMP”) is a typical method for flattening an interlayer insulating film formed on the surface of a semiconductor wafer. However, there are problems accompanying the flattening method performed by CMP. That is, to achieve the target thickness of the interlayer insulating film, the required polishing time varies depending on the following factor. Specifically, the polishing time varies depending on the ratio of the projecting base pattern forming a step on the surface of the interlayer insulating film, with respect to the entire substrate.
An example is illustrated in FIG. 5. A base film 1 is a wiring film including an aluminum material film, a polysilicon film, and an amorphous silicon film. A projecting pattern 3 is formed on the base film 1. An interlayer insulating film 5 is formed on the base film 1 in such a manner as to coat the projecting pattern 3. A projecting part 7 is formed on the surface of the interlayer insulating film 5 due to the projecting pattern 3. In order to polish the interlayer insulating film 5 to attain a desirable film thickness A, the time required for polishing the interlayer insulating film 5 tends to vary depending on the ratio of the size of the projecting pattern 3 with respect to the size of the wafer surface.
Thus, the following procedure has been required in the conventional technology. Specifically, to polish an interlayer insulating film which is formed by coating a projecting pattern, a sample wafer is used for determining the polishing time beforehand. The polishing process is performed on this sample wafer for an appropriate length of time. Then, the thickness of the interlayer insulating film is measured, to determine the desirable polishing time. Subsequently, the wafers in the batch are polished for the determined polishing time.
However, the above method requires a sample wafer for determining the polishing time, and also requires the procedure of determining the desirable polishing time with the use of this sample wafer. Thus, extra steps are necessary for performing this method.
Patent document 1 discloses a chemical mechanical polishing method in an attempt to solve this problem. This method includes a step of defining a formula expressing the relationship between the polishing rate for polishing the interlayer insulating film formed on the wafer and coating the projecting pattern, and the area of the projecting pattern on the wafer. Then, the desirable polishing time is calculated with the use of this formula and the polishing rate for polishing an interlayer insulating film without a projecting pattern.
Patent Document 1: Japanese Patent No. 3745951